非皂化P507大相比萃取富集稀土过程萃余液乳化及稳定机理研究

Mid-heavy rare earths (M-HRE) are the world recognized strategic materials with wide applications. Ion-absorbed rare earth ore is rich in M-HRE and is strategic resource with absolutely competitive advantage in China. The conventional process is disadvantaged by low utilization rate of resources, high consumption of chemical materials, and discharge of large amount of ammonium-nitrogen wastewater and radioactive waste slag, resulting in serious resources and environmental problems. The project is based on the novel technique for the extraction and enrichment of the leaching solution with low rare earth concentration from ion-absorbed rare earth ore using non-saponificated P507 at high phase ratios, and the key problem is the considerable drift loss of the organic phase because of the formation of stable emulsion during the extraction at high phase ratios. For this problem, interdisciplinary methods of surface/interface chemistry, electrochemistry, and metallurgical physical chemistry are employed. The influences of surfactant and solid particle on the formation of emulsion and the stability and surfactivity of the formed emulsion, theoretical calculation of the interaction energies between the emulsion droplets, and the electrochemical parameters fitting of the electric double layer on the surface of the emulsion droplets are investigated to elucidate the formation and stabilization mechanism of emulsion for the extraction and enrichment of rare earth using non-saponificated P507 at high phase ratios. The completion of the project will provide a theoretical basis for the controlled demulsification of the formed emusion during the extraction at high phase ratios and the deep separation of the organic phase from the aquaous phase, further improving the theoretical system for the low-cost, cleaner and efficient extraction of low-concentration rare earth, which has important scientific significance for the green sustainable development of the ion-absorbed rare earth resources.

中重稀土是世界公认的重要战略物资，应用领域广泛。离子型稀土矿富含中重稀土，是我国具有绝对竞争优势的战略资源。现有工艺存在资源利用率低、化工材料消耗高、以及产生大量氨氮废水和含放射性废渣等问题，资源环境问题突出。本项目围绕非皂化P507大相比萃取富集离子型稀土矿低浓度稀土浸出液新技术，针对大相比萃取过程形成稳定乳化液导致大量有机相夹带损失的难题，运用表/界面化学、电化学和冶金物理化学多学科交叉研究方法，开展表面活性物质与固体微粒对乳化液的形成、稳定性及表面活性的影响规律、乳化液滴之间作用能理论计算、以及乳化液滴表面双电层电化学参数拟合研究，揭示非皂化P507大相比萃取稀土过程乳化液的形成与稳定机理。本项目的完成，将为大相比萃取过程乳化液的可控破乳及油/水深度分离提供理论依据，进一步完善低成本、绿色高效萃取富集低浓度稀土新技术的理论体系，对于离子型稀土资源的绿色可持续开发具有重要的科学意义。

离子型稀土矿富含稀缺的中重稀土，而中重稀土是新一代电子信息、现代国防军工等高精尖领域不可或缺的关键原材料。为了解决现有硫酸铵浸取-碳酸氢铵沉淀富集工艺存在的氨氮和放射性废渣污染等突出环境问题，有研集团自主研发成功镁盐体系浸取-连续离心萃取富集稀土新技术。但离子型稀土矿浸出液中REO浓度较低（平均0.3～0.5 g/L），采用非皂化P507在大相比（A/O）条件下萃取富集稀土，所得萃余水相易形成乳化液，不仅使大量有机相夹带而损失，增加生产成本，还可能带来土壤/水体的二次污染风险，因此有必要深入研究大相比萃取过程萃余水相中乳化油滴的稳定机理、破乳机制和破乳行为。.本项目系统研究了非皂化P507大相比萃取富集低浓度稀土过程萃余水相乳化油滴形成与稳定机理，即乳化油滴在萃余水相中的分散度高，表面带负电荷，且上浮速率极其缓慢，难以快速聚并长大；系统研究了Al3+水解作用下萃余水相中乳化油滴的高效破乳机制，即控制萃余水相pH为4～6，使Al3+水解形成Al(OH)3溶胶等而吸附乳化油滴，并在其粘结架桥和网捕卷扫作用下，形成易于沉降的大分子絮体，从而实现破乳；系统研究了Mg(OH)2胶体、大孔型树脂材料等对萃余水相的破乳行为，验证了其破乳的可行性，为萃余水相的可控破乳及油/水深度分离提供理论依据和技术支撑。基于项目研究成果，开展了萃余水相中有机相高效回收扩大试验，处理后萃余水相中磷含量达到1 mg/L左右。项目具有良好的环保、经济和社会效益，应用前景十分广阔。推广应用后，将进一步提高中重稀土战略资源的开发利用水平，促进我国稀土行业绿色高质量发展，巩固我国稀土产业的国际领先地位。